Exoplanet

An extrasolar planet, or exoplanet, is a planet which orbits a star, aside from our own Sun, and therefore belongs to a planetary system aside from the solar system. As of November 2013, over 1000 extrasolar planets have been discovered so far (see List of extrasolar planets).

Extrasolar planets were a subject of speculation for centuries. Astronomers generally supposed that some existed, but it was a mystery how common they were and how similar they were to the planets of our own solar system. The first confirmed detections were finally made in the 1990s when the planet orbiting 51 Pegasi was discovered in 1995 by astronomer Aleksander Wolszczan. Since 2002, more than twenty have been discovered every year. It is now estimated that at least 10% of sunlike stars have planets, and the true fraction may be much higher. The discovery of extrasolar planets raises the question of whether some might support or even permit the development of extraterrestrial life.